Great spotted woodpecker.
You will probably need to squint and use your imagination somewhat, but this is a photo of a great spotted woodpecker! A long way away from my phone camera, on a dull day, through a window and probably with a touch of camera shake. (If you're struggling to see it, it's on the right side of the tree trunk about 3/4 of the way up, level with the bird feeder). Theo spotted it whilst we sat around the breakfast table.